While constructive dismissal is typically the cumulative result of multiple changes in employment conditions, a single change may be enough to trigger it if the change: a. Results in substantially unfavourable terms of employment; and b. Is imposed unilaterally by the employer.
From the tenor of your Q, I’m implying that the change in reporting WAS a unilateral change.
So, then the Q would be what impact will it have on the terms of employment. Simply changing a report sounds pretty harmless. But, of course,without knowing the facts, I can’t really judge how adverse the change is. Key things to ask:
Is the move a demotion? Does it involve a cut in pay or benefits? A loss in prestige? A reduction in responsibilities? Reduced prospects for advancement? An unfavourable change in location or work hours?
The more of these you answer YES to, the stronger the employee’s case for constructive dismissal.
One more thing: Are you sure this is the only change? When employees get together with their lawyers, they can usually brainstorm other adverse changes that you may overlook.
Hope this helps. Glenn